Technology | Tips for using some low molecular weight diols

Low molecular weight diols are multipurpose chemical raw materials. They can be used in polyester resin, polyurethane resin, unsaturated resin, polycarbonate and other synthetic materials, as well as in the synthesis of diacrylate, diglycidyl ether, plasticizer, lubricating oil, etc. The role of low molecular weight diols in polyurethane should not be underestimated. Although different low molecular weight diols have different properties, and after being made into polyester polyols, their properties in polyurethane products vary greatly. The mixed use of different low molecular weight diols will greatly help to improve the performance of polyester polyols. It is very helpful to improve the performance of polyester polyol. It is very helpful to improve the performance of polyester polyol.

1： Commonly used low molecular weight diols are

Ethylene glycol (EG), 1,2-propanediol (1,2-PG), 1,3-butanediol, 1,4-butanediol (BDO, 1,6-hexanediol (HG), neopentyl glycol (NPG), diethylene glycol (DEG), methyl propylene glycol (MPO), dipropylene glycol (DPG), trimethylolpropane (TMP), etc.

2： Main functions of some low molecular weight diols

1) Low molecular diol with symmetrical molecular structure includes ethylene glycol, 1,4-butanediol, 1,6-hexanediol, etc. The polyurethane products made from them have obvious crystallinity.     
2) Low molecular diols with side chain in molecular structure include 1,2-propanediol, diethylene glycol (diethylene glycol), neopentyl glycol, methyl propylene glycol, 1,3-butanediol, 2,4-diethyl 1,5-pentanediol (diethylpentyl glycol DEPD for short), 2-butyl-2-ethyl-1,3-propanediol (BEPD, BEPG for short), octanediol (EHD), etc. Because of the existence of side groups, the polymer is not easy to crystallize and is relatively flexible; It has good hydrolysis resistance. It has good hydrolysis resistance.

3： Characteristics of some low molecular diols with side chain   

The polyurethane resin prepared by mixing 1,2-propanediol and ethylene glycol is amorphous; Diethylene glycol (diethylene glycol) can improve the flexibility of polyurethane adhesive. Dipropylene glycol can also improve the flexibility and corrosion resistance of polyurethane adhesive. Neopentyl glycol can improve the corrosion resistance of polyurethane adhesive, especially alkali resistance and hydrolysis resistance.      
The polyurethane resin synthesized from the above diols is too flexible, and is generally not used alone, but mixed with other corresponding diols. Methyl propylene glycol is the best substitute for neopentyl glycol, l, 6-hexanediol, etc., with a symmetrical molecular structure, but it is cheaper than neopentyl glycol and l, 6-hexanediol.